fix missing dependency in windows build

Author: Federico Fissore

build/windows/launcher/config.xml

@@ -20,6 +20,7 @@
     <cp>lib/jna.jar</cp>
     <cp>lib/ecj.jar</cp>
     <cp>lib/RXTXcomm.jar</cp>
+    <cp>lib/commons-exec-1.1.jar</cp>
   </classPath>
   <jre>
     <path>java</path>